1897, from German Lumpenproletariat (1850), from Marx, who coined it and used it to mean "the rabble, poorest of the working class," "who make no contribution to the workers' cause" [OED]. From German lump "ragamuffin," which is related to lumpen "a rag, tatter," probably ultimately related to English lump (n.). With proletariat. Its secondary sense of "boorish, stupid people" led to lumpen- being taken as a word-forming element meaning "unenlightened."
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